Electrical wire and a method of stripping the insulation thereof

ABSTRACT

An electrical wire has a central electrically conductive member such as copper, aluminum, gold or silver or admixtures or alloys thereof, coated by a photoresistive insulator, preferably of a negative photoresistive material such as polyimide. A non-mechanical method of stripping a desired portion of the length of the insulator from the electrical wire comprises exposing the desired length of the electrical wire to a source of UV light. The UV light then “softens” the insulator which either evaporates or can be dissolved by immersing it in a solvent.

TECHNICAL FIELD

[0001] The present invention relates to an electrical wire and more particularly to an electrical wire which is used in an improved method for stripping a desired length of insulation therefrom to expose the conductive member.

BACKGROUND OF THE INVENTION

[0002] An electrical wire comprising an electrically conductive member with an insulator surrounding the member is well known in the art. Typically, in the prior art, electrical wires are used to electrically connect different electrical or electronic components. In so doing, the insulator surrounding the electrically conductive member must be removed so that the electrically conductive member, typically a metal such as gold, silver, or more commonly copper or aluminum, can then be electrically connected to the electrical or electronic components by solder or the like. In order to remove the insulator which surrounds the electrically conductive member, wire strippers or other mechanical devices have been used. In a wire stripper, a plier like device having a hole with a sharp edge is used. The hole is approximately the size of the electrically conductive member. As the stripper is squeezed or engages the outer insulator, it cuts the outer insulator. However, since there is a hole that is approximately the size of the electrically conductive member, the stripper stops and does not cut into the electrically conductive member. The user then exerts a force by pulling the insulator away. Sometimes, in the process of so doing, the stripper could hit or nick the electrically conductive member. In other cases, the pulling may cause tear in the insulator coating, thereby stripping more or less than the desired amount. Other mechanical methods for stripping the insulation include the use of a knife to cut the insulation and then pull the cut insulation. However, the problems of potential nicking the electrically conductive member and the inaccuracy of the amount of insulation stripped remains. Still other methods have included the use of sand paper or other abrasive technique to remove the insulation.

[0003] The aforementioned problems of stripping an electrical wire is exacerbated as the size of the wire decreases. As the wires become smaller and smaller to connect smaller components or used in confined spaces, the electrically conductive member becomes extremely small and the insulator surrounding it is also very small. Thus the tolerance between the outer diameter of the electrical wire and the outer diameter of the electrically conductive member is very small. This increases the risk that using a stripper or other mechanical means can nick or cut the electrically conductive member and/or the mechanical device can remove more or less of the insulator than is desired.

SUMMARY OF THE INVENTION

[0004] An electrical wire comprises an electrically conductive member with a photoresistive insulator coating the member.

[0005] The present invention also relates to a method of stripping a desired length of insulator from an electrical wire. The wire has an electrically conductive member and an insulator coating the member. The insulator is a negative photoresistive material which is sensitive to UV light. The method of stripping comprises exposing the desired length of the wire to a source of UV light sufficient to dissipate the desired length of insulator. Alternatively, the method comprises exposing the desired length of the wire to a source of UV light and then immersing the exposed wire in a solvent to dissolve the desired length of the photoresistive material.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 is a perspective view of an improved electrical wire of the present invention.

[0007]FIG. 2 is a perspective view of the method of the present invention to strip a desired length of insulator from an electrical wire.

DESCRIPTION OF THE INVENTION

[0008] Referring to FIG. 1 there is shown an electrical wire 10 of the present invention. The electrical wire 10 comprises an electrically conductive member 12. Typically, the electrically conductive member 12 is a metal and is selected from a group consisting of gold, silver, copper, aluminum, or admixtures thereof or alloys thereof. The electrically conductive member 12 can also comprise a strand which is a plurality of small wires made from any of the foregoing described metals. Surrounding the electrically conductive member 12 is a photoresistive insulator 14 coating the member 12. The photoresistive insulator 14 in the preferred embodiment is a negative photoresistive material which is sensitive to UV light. A negative photoresistive material means a material which when exposed to the appropriate light source becomes soft and either dissipates in the atmosphere or when immersed in a solvent dissolves. Otherwise, the remaining portion of the photoresistive material, i.e., those portions which have not been exposed to the appropriate light source, will not dissipate into atmosphere nor will they dissolve in the solvent. In a preferred embodiment, the negative photoresistive material is a material made from polyimide and is a material such as a commercially available chemical designated as SU-8 100 or photoresist solder mask. Further, the light source to which the photoresistive insulator 14 is sensitive is in the UV light range. One example is to expose the wire 10 to a dose of 610 mJ/cm². After the wire 10 is exposed, it is immersed in an SU-8 developer, which is PM acetate, and stirred for about 25 minutes. The insulator is removed by the development process. The wire 10 is then rinsed using isopropyl alcohol and dried with air or nitrogen. Further, it has been found that the method of the present invention can be used with both positive or negative photoresist material as the insulator 14.

[0009] Referring to FIG. 2, there is shown a step in the method of the present invention. In the method of the present invention, a desired length 16 of the wire 10 of the present invention is to be stripped of the insulator 14. The desired length 16 of the wire length 10 is exposed to a UV light 20. In a preferred embodiment, a blocking panel 18 serves to block the rest of the wire 10 from the exposure of the UV light 20. Thus, for example, the panel 18 can be a box and the UV light 20 can be contained within the box 18 and the wire 10 inserted through an aperture into the box 18 such that a desired length 16 is placed inside the box 18. When the UV light 20 is activated, the desired portion of the wire 10 is then exposed inside the box 18.

[0010] As previously described, the insulator 14 is preferably made of a negative photoresistive material, such as polyimide. If the insulator 14 is sufficiently thinly coated about the electrically conductive member 12, it is possible that upon exposure to the UV light 20, the desired portion 16 will soften and will dissipate into the atmosphere. On the other hand, if the insulator 14 is thick, then after the desired portion 16 is exposed to the UV light 20, the wire 10 is immersed in a solvent. The solvent would dissolve that portion of the insulator 16 which has been exposed to UV light. The solvent would not dissolve the portion of the insulator 14 not exposed to UV light, even if it were immersed in the solvent.

[0011] From the foregoing it can be seen that a “clean” and non-mechanical method of removal of a desired length of an insulator about an electrical wire is disclosed. Further, an improved electrical wire is also disclosed. The improved electrical wire can be easily manufactured since the electrically conductive member 12 is well known and is of conventional design. The electrically conductive member 12 is simply “dipped” into a liquid solution of the insulator 14 which is of the requisite photoresistive properties. 

What is claimed is:
 1. An electrical wire comprising: an electrically conductive member; and a photoresistive insulator coating said member.
 2. The wire of claim 1 wherein said electrically conductive member is a metal selected from a group consisting of gold, silver, copper, aluminum, or admixtures or alloys thereof.
 3. The wire of claim 1 wherein said photoresistive insulator is a negative photoresistive material, sensitive to UV light.
 4. The wire of claim 3 wherein said photoresistive material is made from polyimide.
 5. The wire of claim 3 wherein said photoresistive material evaporates upon exposure to UV light.
 6. The wire of claim 3 wherein said photoresistive material dissolves in a solvent after exposure to UV light.
 7. A method of stripping a desired length of insulator from an electrical wire, with said wire having an electrically conductive member and with said insulator coating said member, said insulator being a negative photoresistive material, sensitive to UV light, said method comprising: exposing said desired length of said wire to a source of UV light sufficient to dissipate said desired length of insulator.
 8. A method of stripping a desired length of insulator from an electrical wire, with said wire having an electrically conductive member and with said insulator coating said member, said insulator being a negative photoresistive material, sensitive to UV light, said method comprising: exposing said desired length of said wire to a source of UV light; and immersing said exposed wire in a solvent to dissolve said desired length of said photoresistive material. 